Variable-gradient method for adaptive equaliser

A simple technique for the implementation of an adaptive equaliser is a gradient-seeking method. Two critical parameters associated with adaptive equalisation are the rate of convergence and the steady-state mean-square error attainable. When a fixed gradient is used in the gradient-search procedure for an adaptive equaliser, rapid convergence and a small steady-state mean-square error are two conflicting requirements. Use of a variable gradient parameter at each iteration provides a good compromise. A method for iteratively computing the gradient parameter is introduced, so that the random walk in the gradient-search procedure is executed, on the average, with decreasing step size as the iterative algorithm converges.     

Code-aided adaptive equaliser for mobile communication systems

A new structure for a code-aided adaptive equaliser is proposed for mobile communication systems. The structure aims to improve the tracking capability of a receiver that combines equalisation and coding. Simulation results show that the code-aided adaptive equaliser performs particularly well over mobile channels that fade at a moderate rate. Compared to a conventional equaliser, an order of magnitude reduction in bit error rate is achieved     

Convergence of adaptive equaliser for data transmission

A faster algorithm is proposed to determine the optimal tap setting of transversal delay-line equalisers which use the criterion that the mean-square error is minimum. The convergence of this algorithm is compared with the well known steepest-descent algorithm.     

Fuzzy adaptive decision feedback equaliser

As a new approach to the equalisation of nonlinear channels, a fuzzy adaptive decision feedback equaliser based on a fuzzy adaptive filter is proposed. With perfect knowledge of the channel, the proposed method not only improves equalisation performance but also reduces the computational complexity compared with the conventional fuzzy adaptive filter     

New adaptive equaliser with infinite impulse response

A new adaptive equaliser with an infinite impulse response (i.i.r.) which is implemented with a least-mean-square-error (l.m.s.e.) algorithm is described. The approximation of an ideal impulse response function by a linear combination of exponential functions is used in its design, with some advantage in its performance.     

Integrated hybrid adaptive space-time equaliser for interferencerejection in multipath DS/CDMA systems

An integrated hybrid space-time equaliser is proposed for interference suppression in DS/CDMA systems. It outperforms the existing time-domain-only counterpart, and previous work on the integrated space-time receiver in terms of MSE and near-far resistance. A comparison between simulation and analytical results is also presented     

Performance of adaptive multisensor decision feedback equaliser fortime-varying frequency selective radio channels

A multisensor decision feedback equaliser based on the minimum mean squared error (MMSE) criterion is studied. The superiority of the performance of the multisensor equaliser is shown by simulation of a whole communication system in which the adaptive equaliser is incorporated. The recursive least squares (RLS) algorithm is used to update the coefficients. From the results obtained for a time-varying urban terrain channel model, the extremely interesting tracking capability of the multisensor equaliser is shown     

OFDM for broadcasting in presence of analogue co-channelinterference

This paper treats the problems of digital TV terrestrial broadcasting in presence of co-channel interference from analogue TV services. The channel capacity is calculated for the optimum distribution of the transmitted power. An OFDM scheme is presented which is designed to be robust to the analogue TV interference. Power and number of bits per symbol are assigned to each OFDM channel to give the maximum data rate for a given signal to interference ratio. Simulations of the proposed scheme, for 8 MHz bandwidth and interference from a system G PAL signal, show that acceptable error rate can be achieved for e.g. 27 Mbit/s and 39 Mbit/s at signal to interference ratios of -6 dB and 0 dB, respectively. The proposed scheme is suitable for the next generation terrestrial TV networks which are going to coexist with the current analogue systems     

Adaptive equaliser for multipath channels

An adaptive equalising system is described which makes possible efficient communication of serial digital data over a multipath channel, within certain limitations of the severity of the multipath. This technique is particularly suitable for two paths of comparable strength.     

Pre-FFT equaliser design for OFDM

Orthogonal frequency division multiplexing (OFDM) transmission in a time dispersive radio channel requires the insertion of a guard interval to combat inter-carrier interference. This insertion of the guard interval reduces the transmission efficiency. The pre-FFT equaliser design presented supplements or replaces the guard interval and thereby achieves a more efficient transmission     

Reduced-complexity equaliser for nonlinear channels

The generalised cerebellar model arithmetic computer (GCMAC) network is applied to the problem of adaptive equalisation of nonlinear channels. The GCMAC-based equaliser is compared with other well-known structures such as the Volterra filter and the multi-layer perceptron. The results obtained show the effectiveness of the proposed structure for compensating strong nonlinearities     

Extended RLS lattice adaptive filters

This paper solves the problem of developing exact fast weighted RLS lattice adaptive filters for input signals induced by general orthonormal filter models. The resulting algorithm can be viewed as a counterpart of the extended fast fixed-order RLS adaptive filters previously derived.     

Magnetostatic-wave group-delay equaliser

The application is described of magnetostatic wave delay lines to group-delay equalisation at intermediate frequencies of millimetric circular-waveguide lengths utilised in high-data-rate digital communication systems. Experimental results and theory have shown that suitable bias-field-adjustable-delay/frequency characteristics can be realised using surface-wave propagation in thick yttrium-iron garnet (y.i.g.) films grown by liquid-phase epitaxy.     

Extended fast fixed-order RLS adaptive filters

The existing derivations of conventional fast RLS adaptive filters are intrinsically dependent on the shift structure in the input regression vectors. This structure arises when a tapped-delay line (FIR) filter is used as a modeling filter. We show, unlike what original derivations may suggest, that fast fixed-order RLS adaptive algorithms are not limited to FIR filter structures. We show that fast recursions in both explicit and array forms exist for more general data structures, such as orthonormally based models. One of the benefits of working with orthonormal bases is that fewer parameters can be used to model long impulse responses     

Automatic selective equaliser for telephone facsimile transmission

A simple automatic equaliser designed especially for G2 as well as G1 facsimile signals received through carrier links is presented. The new method requires no additional signal, utilising only a phasing signal to fix the equalising parameters by detecting the symmetry in the received step response.     

Complexity reduction for a multisensor Viterbi equaliser

A multisensor equaliser based on the Viterbi algorithm is presented. The equaliser consists of a multisensor Viterbi estimator and adaptive channel estimators. Its complexity is described and its performance over mobile channels is analysed. It is concluded that the multisensor Viterbi equaliser is capable of considering truncated channels, thereby allowing a considerable reduction in complexity     

Simple non-coherent equaliser for the DECT system

A non-coherent equaliser structure suitable for DECT-type systems is introduced which performs equalisation at the output of a differential detector. It employs a two-state Viterbi algorithm using a simple channel estimation process. Performance assessments are presented which suggest that the new receiver can yield significant improvements with respect to standard non-coherent receivers in dispersive channels. At the same time, unlike coherent equaliser structures, it remains largely unaffected by both modulation index drifts and frequency offsets     

MLP equaliser for frequency selective time-varying channels

A multilayer perceptron based equaliser with RLS adaptation algorithm is presented. Its performance is evaluated in a communications system using GMSK modulation with frequency selective Rayleigh fading channel of six paths. A bit error rate performance comparison shows that the MLP structure has better performance than the traditional decision feedback equaliser     

Fast converging LMS equaliser

A simple and efficient method is presented that makes use of a predictor to reduce the eigenvalue spread (ES) of the input signal for improving the convergence rate of the least mean square (LMS) adaptive equaliser. The performance is analysed by using a Gaussian assumption and is shown to be in good agreement with the simulations.<>